Artificial leather fabrication



Patented Feb. 2, 1932 UNITED, STATES PATENT OFFICE GEORGE A. RICHTER AND WALLACE B. VAN ARSDEL, OF IBERLI N, NEW HAMPSHIRE.

ASSIGNORS '.[0 BROWN COMPANY, OF BERLIN, NEW HAMPSHIRE,'A CORPORATION OF MAINE No Drawing. I

This invention deals with the fabrication of artificial leather, its object being to produce a product which, while useful in various fields, as in making upholstered furniture,

automobile tops, travelling bags, and the like, is more particularly designed for use in making shoe parts, such as inner soles.

' 4 Artificial leather shoe parts, in order to be acceptable by the trade, must have characteristics closely resembling the natural product. For example, an artificial leather innersole should have high flexibility, tensile strength, and tear resistance, and should be resilient and of sufficient porosity to permit breathing of the foot and to absorb perspiration therefrom. It has been found that a satisfactory article may be obtained by impregnating a foundation of loosely felted cellulose fiber with a rubber-carrying liquid vehicle such as so-called rubber solutions in organic solvents or aqueous dispersions of'rubber, and then removing the liquidvehicle, and if desired, A

vulcanizing the rubber-impregnated product.

U on'the removal of the liquid vehicle, the 95 ru ber serves to bind together the fibers of the foundation and suficient porosity is restored thereto so that it is capable of readily absorbing moisture. When a highly porous web of loosel felted cellulose fiber is used as a foundation and the dried, rubber-impregnated product contains about 90% to 011.0% rubber solids, based on the weight of dry fiber, ithas been found that the product has the all-round characteristics sought for in articles such as innersoles. It is sometimes desired to coat the innersole with materials such as lacquers, in order to obtain such qualities as gloss and smoothness to the foot.

If an innersole of the type hereinbefore ribed is coated with a lacquer, considerable porosity and resilency is lost, since the lacquer penetrates into and fills the pores of the sole. We have observed that a comparatively small change in the. rubber content of such soles is associated with an unexpectedly great change in characteristics such 'as tensile strength, tear. resistance, and

orosity. For instance, a sole having a rubber content of about 70 based on the weight of dry fiber, is notably inferior in strength ARTIFICIAL LEATHER FABRICATION Application filed September 27, 1929. Serial No. 395,744.

to a similar sole having a rubber content of about 110%, but we have further observed that the sole of lower rubber content may be coated with material such as lacquers without becoming so lackingin porosity and resiliency as the sole of higher rubber content.

In accordance with the present invention we produce a rubber-impregnated sheet of interfelted cellulose fibers, a surface portion of which is of lower rubber content than the rest of the sheet, so that when the surface of this portion is coated or dressed with materials such as lacquers, undesirable change in characteristics such as porosity and resiliency will be minimized, and the resulting product will have the desired high strength and at the same time be free from the objectionable rubbery feel experienced when the surface portion contains a large amount of rubber. In makin an artificial leather suitable for use in ma ring shoe parts such as innersoles, this may be accomplished by bonding together one or more porous, rubberimpregnated webs with another porous, rubber-impregnated web having lower rubber content and higher porosity as the surface ply, the surface of the latter ply bein coated with a material such as a lacquer. hile it is not absolutely necessary, it is preferable to coat the surface ply and to emboss it before it is united to the rest of the material.

This is especially the case if any embossing is i done because the high pressure of an embossing press would tend to roduce a very high A procedure which may be followed in producing the product of the resent invention, may be substantially as ollows. v web com osed of loosely interfelted cellulose fibers an possessing high porosity is preferably used as the foundation for allthe plies. 1'

A web of unusually high porositymay be produced by using a substantially unbeaten wood fiber of high alpha cellulose content say, 94% or greater, as a raw material, an

about 70%.

forming such fiber into a web on a papermaking machine designed to efiect dewatermg and drying of the web without the application of the heavy pressures used in ordinary papermaking practice. While other fibers in substantially unbeaten condition, such as sulphite, kraft, or soda pulp, may be employed, a substantially unbeaten wood fiber of high alpha cellulose content is preferred, because it is more highly absoptive than the usual unbeaten commercial wood fibers, and hence enhances the absor tivity or porosity resulting from the loosely elted, uncompacted condition of the fibers. The dry, porous web may be passed through a bath of rubber-carrying vehicle such as an ammoniapreserved latex diluted to a solids content of, say, about 16%, at which content immersion for aboutfive to thirt seconds effects a thorough impregnation 0 the web. If to be used as the outer plies of the sole, the im regnated web may be squeezed until its rub er solids content is about 110%, based on the weight of dry fiber, and if to be used as the inner or surface plies, until its rubber solids content is The rubber content of the inner plies may be reduced not only by squeezing them harder but also by diluting the latex further, say, to 14% instead of 16% solids content. In order to prevent migration of the rubber globules to the surface of the web during drying, the ammonia-preserved latex may be treated with the oxide of an amphoteric metal, preferably zinc oxide, as descrlbed in application Serial No. 369,267, filed June 7, 1929, by Roger B. Hill, or with alkaline earth metal hydroxides, preferably slaked lime, as described in application Serial No.

r 373,055, filed June 22, 1929, by Roger B. Hill.

When slaked lime is the compound added to the latex to overcome migration tendencies during drying, protective colloids such as soluble soaps or caseinates which are capable of being precipitated by lime as insoluble calcium soaps or caseinates, are preferably added to the latex prior to the addition of the slaked lime in order to overcome coagulating tendencies. Such treatment of the latex prior to its use for the impregnation of the web makes possible the production of a dried, rubber-impregnated web of uniformity in respect of rubber distribution therethrough, as troublesome non-rubber constituents ofthe latex,

. namely, the proteins and the resins, are converted to an insoluble, inert condition. parently, setting or coagulation of the rubber by drying is so retarded by the proteins and resins which exist respectively in an armmonia-preserved latex as water-soluble proteinates and alkali resinates, that there is' a tendency for rubber particles to migrate-to the surface of the impregnated product,

where evaporation of water is taking place.

The tendency for migration of rubber particles is especially pronounced in the case of lacquer being preferable, Ap-

highly porous webs of cellulose fiber of the type described, evidently because of the high capillary action taking place during drying to cause such migration. When such compounding agents as lime and casein are used, the ratio-of total impregnating solids to fiber may with advantage be raised from, say, 110% to 115%, or even to 200%, based on dry fiber. In such a case, however, the actual ratio of rubber to fiber would still not be much above 110%, since a composition as low 1n rubber content as 60% may be useds" If desired, a vulcanized latex may be used, so that when the latex-impregnated web is subsequently dried, the rubber will be coagulated in the web in vulcanized condition. 0r artificial aqueous dispersions may be used in lieu of natural latex. Suitable rubber-compounding materials, vulcanizing agents, and accelerators of vulcanization may be added to the artificial or natural rubber dispersion, so that the dried, rubber-impregnated web may be vilcanized under the action of heat, if desire The web usedas a foundation material is preferably comparatively thin, so that it may be impregnated rapidly and uniformly. In actual practice, a web of about 100 ounds basis weight (i. e., the weight of 28 80 sq. ft. of web) may be employed to good advantage. The impregnated web is of insufficient thickness for the manufacture of products such as innersoles, it being necessary to bond together two or more sheets. ()ne or more sheets impregnated to a rubber content of about 110%, and a sheet impregnated to a rubber content of about 90% may be bonded together by latex, the sheet of lower rubber content constituting a surface ply of the resulting product. It has been found advantageous to moisten or wet the surfaces of the dried, rubber-i pregnated sheets and then toapply a comparatively thick or concentrated latex as the bonding material, whereupon the sheets may be superposed, united under pressure, and dried. Apparently, the initial moistening or wetting of the plies promotes penetration of the thick latexinto the surface portion of the plies and results in a better interlocking of the plies after the latex is dried.

The inner ply may be surfaced with a suitable coating material, a nitrocellulose because it imparts desirable gloss and smoothness to the foot, and is permanent against the action of perspiration. Nitrocellulose lacquer, while referable, is not by any means the only finish which may be used. Other finishes such as are used on kid and sheep skins may be applied .where gloss and color are much more important than permanence. The lacquer may be applied as by. spraying, upon the coated product may be dried. If desired, the lacquered surface may be emfaced with a coating material.

bossed, preferably before uniting with the other plies, to produce grain eifects simulating those of natural leather.

The surface treatment may include steps in addition to those hereinbefore given. For instance, an initial or base coat of clear nitrocellulose lacquer may be applied to the surface of the sheet, whereupon one or more coats of nitrocellulose lacquer containing suitable pigments or fillers may be applied. The base coat prevents sinking of the pigments or fillers into the rubber-impregnated foundation, where they are undesirable- The lacquered and pigmented surface may then be embossed and a final coat of clear nitrocellulose lacquer may be applied thereto. The lacquered surface may then be smooth-plated to destroy the oily or greasy appearance and to bring out the gloss. The finished product may then be united with the other plies and cut into innersoles or used in making other articles where artificial leather having the characteristics of such a product is desired.

We claim:

1. An artificial leather comprising a rubber-impregnated sheet of interfelted cellulose fibers having a'surface portion of lower rubber content than the rest of the sheet.

2. An artificial leather comprising a rub her-impregnated sheet of interfelted cellulose fibers having a surface portion of lower 7. A method which comprises im regnating a plurality of webs of cellulose bers with a rubber-carrying liquid vehicle to different rubber contents, removing the liquid vehicle, applying lacquer tothe surface of the ply of low rubber content, embossing the lacquered surface to the desired grain effect, superposing and uniting, it. as a surface ply with the other rubber-impregnated webs, and cutting into innersoles.

8. An artificial leather comprising a rubber-impregnated, loosely interfelted, paper machine-made foundation of wood fibers of high alpha-cellulose content having a surface portion of lower rubber content than the rest of the foundation.

In testimony whereof we have aflixed our signatures. I GEORGE A. RICHTER. WALLACE B. VAN ARSDEL.

rubber content than the rest of the sheet and surfaced at said portion with a coat-' ing material.

3. An innersole comprising a pluralit of superposed, rubber-impregnated plies of interfelted cellulose fibers, the rubber content of the inner ply being lower than the ru ber content of the other plies.

4. An innersole comprislng a pluralit of superposed, rubber-impregnated lies 0 interfelted cellulose fibers bonde together with rubber, the rubber content of the inner ply being lower than the rubber content of the other plies, said inner ply being sur- 5. An innersole comprising a plurality of su erposed, rubber-impregnated plies of inter elted cellulose fibers bonded together with rubber, the solids content including rubber of the inner ply being about 70% to 90%, based on the weight of dry fiber and the solids content including rubber throughout the other plies being about 110% to 200%, said inner ply being surfaced with nitrocellulose lacquer and embossed to the desired grain-effect.

6. A method which comprises superposing and bonding together a plurality of rubber-impregnated webs of, interfelted cellu-' lose fibers of diiferent rubber contents with the web of low rubber content as an outer ply and the surface of which outer ply is finished with a coating material. 

